This invention relates to a flame arrester arrangement for a marine propulsion engine and more particularly to a location for the components of a marine propulsion engine that permits a compact assembly and yet effective flame protection and induction efficiency.
Conventionally many types of marine watercraft are powered by internal combustion engines and particularly engines based upon automotive engines which are modified so as to suit marine application. As a result of this use of automotive type engines and for a variety of other reasons, the layout of certain components of the engine is not optimum for all aspects of engine performance. This may be best understood by reference to FIG. 1 wherein a conventional type of prior art marine propulsion engine is shown and is mounted in the hull of an associated watercraft which is shown partially in cross section and which is identified generally by the reference numeral 11. The engine, indicated generally by the reference numeral 12, is mounted within the hull 11 and forwardly of a transom 13 for driving an outboard drive type of propulsion unit (not shown) in a conventional manner.
The engine 12 includes a cylinder block 14 having a pair of inclined cylinder banks to which cylinder heads 15 are affixed in a known manner. An induction system, indicated generally by the reference numeral 16 is provided for delivering a fuel/air charge to the engine 12. The induction system 16 includes a forwardly facing air inlet and flame arrester 17 which supplies atmospheric air to a plenum chamber 18 which, in turn, serves the individual chambers of the engine through an intake manifold 19 having a plurality of individual runners that serve the cylinders of the engine.
Each cylinder bank is provided with an exhaust manifold 21 which delivers the exhaust gases upwardly to an exhaust elbow 22 that is disposed at the respective side of the engine. The exhaust elbows 22, in turn, deliver the exhaust gases to a "Y" pipe 23 having a discharge end 24 that communicates with an underwater exhaust gas discharge of the outboard drive unit.
The engine 12 is also water cooled and its temperature is maintained by a thermostat contained within a thermostat housing 25 disposed in the valley between the cylinder banks and at the forward end of the engine. Normally a throttle body 26 is provided directly above the thermostat housing 25 for controlling the air flow from the inlet device and flame arrester 17 into the plenum chamber 18.
As will be seen from the drawings, the plenum chamber 18 is disposed so that its lower periphery is lower than the upper periphery of the exhaust elbows 22 and this limits the transverse outwardly extending width of the plenum chamber 18. Furthermore, the inlet device 17 is positioned forwardly of the thermostat housing 25 and depends slightly below it. This disposition means that the air flow must flow radially into the inlet device 17 and then turn through 90.degree. to enter the throttle body 26, thus limiting the size of the inlet device 17 and also restricting the air flow. In addition, the inlet device 17 then must extend beyond the end of the engine and specifically beyond the thermostat housing 25 so as to increase the length "L" of the engine while at the same time providing a relatively great height "H".
From the foregoing description of the prior art type of devices, it should be readily apparent that there are a number of compromises in the layout of the components which increase the overall size of the engine, decreases the induction efficiency and also somewhat restricts the flame arrester performance for the engine.
It is, therefore, a principal object of this invention to provide an improved flame arrester arrangement for a marine propulsion engine.
It is a yet further object of this invention to provide an improved induction system and other layout components for a marine engine that provides a compact engine, high induction efficiency and good flame arresting control.